1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Sound waves(phase difference) PLS. HELP

  1. Jun 13, 2009 #1
    sound waves(phase difference) URGENT PLS. HELP

    1. The problem statement, all variables and given/known data

    2 speakers ,in phase, have a frequency of 170Hz [so lambda= 2m; the speed of sound is 340 m/s] As you move along the x axis, where is the sound:
    a)a minimum (compared to nearby pts.)
    b)a maximum (compared to nearby pts.)

    2. Relevant equations

    r2-r1=delta r

    3. The attempt at a solution

    so for a) i know that there shld be no sound and that occurs the 1st minimum @ lambda/2

    so i did r2-r1 =lamda/2
    r2=sqrt(64+r1^2) therefore

    sqrt(64+r1^2)-r1=2/2

    and this is where i am stuck everytime i open it up the r1 gets cancelled or i have r1^2-r1=-63 ..i'm supposed to be getting an r1= 31.5 m ..please help
     

    Attached Files:

  2. jcsd
  3. Jun 13, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Re: sound waves(phase difference) URGENT PLS. HELP

    So far, so good.

    Show how you got this.
     
  4. Jun 13, 2009 #3
    Re: sound waves(phase difference) URGENT PLS. HELP

    sqrt(64+r1^2)-r1=2/2
    sqrt(64+r1^2)-r1=1[if i move the sqrt over]
    64+r1^2-r1 =1^2
    r1^2-r1= -63

    the other way i did it was
    sqrt(64+r1^2)-r1=2/2 [if i take the sqrt ]
    8+r1-r1= 1
    in the last one r1's cancel leaving me w/8=1
     
  5. Jun 13, 2009 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Re: sound waves(phase difference) URGENT PLS. HELP

    OK.
    :yuck: (You didn't square the left hand side properly.)

    How about:
    sqrt(64+r1^2)-r1=1
    sqrt(64+r1^2) = 1+r1
    (continue...)
     
  6. Jun 13, 2009 #5
    Re: sound waves(phase difference) URGENT PLS. HELP

    so if i continue with your line of thinking
    sqrt(64+r1^2) = 1+r1
    64+r1^2=1+r1^2
    but if i move it over to get the like terms together wouldnt the r1's still cancel??
     
  7. Jun 13, 2009 #6

    Doc Al

    User Avatar

    Staff: Mentor

    Re: sound waves(phase difference) URGENT PLS. HELP

    This time you didn't square the right hand side properly.

    What's (1 + r1)^2?
    (1 + r1)*(1 + r1) = ?

    (Work that out.)
     
  8. Jun 13, 2009 #7
    Re: sound waves(phase difference) URGENT PLS. HELP

    thank you so much i was beating my head in the whole time and the mistake was so stupid and silly..thanks again
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Sound waves(phase difference) PLS. HELP
Loading...